Hibernate（五）

注解高级（原文再续书接上一回）

7.继承映射

第一种：InheritanceType.JOINED 查询时会出现很多join语句.

 package com.rong.entity.joined;

 import javax.persistence.Entity;
 import javax.persistence.GeneratedValue;
 import javax.persistence.GenerationType;
 import javax.persistence.Id;
 import javax.persistence.Inheritance;
 import javax.persistence.InheritanceType;
 import javax.persistence.Table;

 @Entity
 @Table(name="person")
 //所有的持久化都会生成表(子类表会引用父类表的主键列)
 //每个类都会生成一张表
 //子类的表中会默认引用父类中的id
 @Inheritance(strategy=InheritanceType.JOINED)
 public class Person {
     @Id
     @GeneratedValue(strategy=GenerationType.AUTO)
     private int id;
     private String name;
     private int age;
     public int getId() {
         return id;
     }
     public void setId(int id) {
         this.id = id;
     }
     public String getName() {
         return name;
     }
     public void setName(String name) {
         this.name = name;
     }
     public int getAge() {
         return age;
     }
     public void setAge(int age) {
         this.age = age;
     }
     @Override
     public String toString() {
         return "Person [id=" + id + ", name=" + name + ", age=" + age + "]";
     }
 }

 package com.rong.entity.joined;

 import javax.persistence.Entity;
 import javax.persistence.Table;

 @Entity
 @Table(name="student")
 public class Student extends Person{
     private String number;

     public String getNumber() {
         return number;
     }

     public void setNumber(String number) {
         this.number = number;
     }
 }

 package com.rong.test;

 import org.hibernate.Session;
 import org.hibernate.SessionFactory;
 import org.hibernate.Transaction;
 import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
 import org.hibernate.cfg.Configuration;
 import org.hibernate.service.ServiceRegistry;
 import org.junit.Test;

 import com.rong.entity.joined.Person;
 import com.rong.entity.joined.Student;

 public class HibernateTest {
     @Test
     public void test1(){
         Configuration configuration=new Configuration().configure();
         ServiceRegistry serviceRegistry=new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build();
         SessionFactory sessionFactory = configuration.buildSessionFactory(serviceRegistry);
         Session session = sessionFactory.openSession();
         Transaction transaction = session.beginTransaction();
         //插入
         Student student=new Student();
         student.setAge(18);
         student.setName("悠悠");
         student.setNumber("654321");
         session.save(student);
         //查询
         Person person=(Person)session.get(Person.class, 1);
         System.out.println(person);
         Student stu=(Student) session.get(Student.class, 1);
         System.out.println(stu.getId()+":"+stu.getName()+":"+stu.getNumber());
         transaction.commit();
         session.close();
         sessionFactory.close();
     }
 }

第二种：InheritanceType.SINGLE_TABLE 所有子类属性中不能加非空约束

 package com.rong.entity.singletable;

 import javax.persistence.DiscriminatorColumn;
 import javax.persistence.DiscriminatorType;
 import javax.persistence.DiscriminatorValue;
 import javax.persistence.Entity;
 import javax.persistence.GeneratedValue;
 import javax.persistence.GenerationType;
 import javax.persistence.Id;
 import javax.persistence.Inheritance;
 import javax.persistence.InheritanceType;
 import javax.persistence.Table;

 @Entity
 @Table(name="person")
 @Inheritance(strategy=InheritanceType.SINGLE_TABLE)// 单个表
 @DiscriminatorColumn(name="dc",discriminatorType=DiscriminatorType.INTEGER)//辨别者列
 @DiscriminatorValue(value="0")// 辨别者列值
 public class Person {
     @Id
     @GeneratedValue(strategy=GenerationType.AUTO)
     private int id;
     private String name;
     private int age;
     public int getId() {
         return id;
     }
     public void setId(int id) {
         this.id = id;
     }
     public String getName() {
         return name;
     }
     public void setName(String name) {
         this.name = name;
     }
     public int getAge() {
         return age;
     }
     public void setAge(int age) {
         this.age = age;
     }
     @Override
     public String toString() {
         return "Person [id=" + id + ", name=" + name + ", age=" + age + "]";
     }
 }

 package com.rong.entity.singletable;

 import javax.persistence.DiscriminatorValue;
 import javax.persistence.Entity;
 import javax.persistence.Table;

 @Entity
 @Table(name="student")
 @DiscriminatorValue(value="1")// 辨别者列值
 public class Student extends Person{
     private String number;

     public String getNumber() {
         return number;
     }

     public void setNumber(String number) {
         this.number = number;
     }
 }

 package com.rong.test;

 import org.hibernate.Session;
 import org.hibernate.SessionFactory;
 import org.hibernate.Transaction;
 import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
 import org.hibernate.cfg.Configuration;
 import org.hibernate.service.ServiceRegistry;
 import org.junit.Test;

 import com.rong.entity.singletable.Person;
 import com.rong.entity.singletable.Student;

 public class HibernateTest {
     @Test
     public void test1(){
         Configuration configuration=new Configuration().configure();
         ServiceRegistry serviceRegistry=new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build();
         SessionFactory sessionFactory = configuration.buildSessionFactory(serviceRegistry);
         Session session = sessionFactory.openSession();
         Transaction transaction = session.beginTransaction();
         //插入
         Student student=new Student();
         student.setAge(16);
         student.setName("晓晓");
         student.setNumber("3824");
         session.save(student);
         Person person=new Person();
         person.setAge(19);
         person.setName("达达");
         session.save(person);
         //查询
         Person per=(Person)session.get(Person.class, 2);
         System.out.println(per);
         Student stu=(Student) session.get(Student.class, 1);
         System.out.println(stu.getId()+":"+stu.getName()+":"+stu.getNumber());
         transaction.commit();
         session.close();
         sessionFactory.close();
     }
 }

第三种：InheritanceType.TABLE_PER_CLASS 这种策略主键不能用自增长.查询时会出现union运算.

 package com.rong.entity.tableperclass;

 import javax.persistence.Entity;
 import javax.persistence.Id;
 import javax.persistence.Inheritance;
 import javax.persistence.InheritanceType;
 import javax.persistence.Table;

 @Entity
 @Table(name="person")
 //所有的持久化都会生成表(子类会把父类中的属性继承过来生成在自己的表中)
 @Inheritance(strategy=InheritanceType.TABLE_PER_CLASS)
 public class Person {
     @Id
     private int id;
     private String name;
     private int age;
     public int getId() {
         return id;
     }
     public void setId(int id) {
         this.id = id;
     }
     public String getName() {
         return name;
     }
     public void setName(String name) {
         this.name = name;
     }
     public int getAge() {
         return age;
     }
     public void setAge(int age) {
         this.age = age;
     }
     @Override
     public String toString() {
         return "Person [id=" + id + ", name=" + name + ", age=" + age + "]";
     }
 }

 package com.rong.entity.tableperclass;

 import javax.persistence.Entity;
 import javax.persistence.Table;

 @Entity
 @Table(name="student")
 public class Student extends Person{
     private String number;

     public String getNumber() {
         return number;
     }

     public void setNumber(String number) {
         this.number = number;
     }
 }

 package com.rong.test;

 import org.hibernate.Session;
 import org.hibernate.SessionFactory;
 import org.hibernate.Transaction;
 import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
 import org.hibernate.cfg.Configuration;
 import org.hibernate.service.ServiceRegistry;
 import org.junit.Test;

 import com.rong.entity.tableperclass.Student;
 public class HibernateTest {
     @Test
     public void test1(){
         Configuration configuration=new Configuration().configure();
         ServiceRegistry serviceRegistry=new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build();
         SessionFactory sessionFactory = configuration.buildSessionFactory(serviceRegistry);
         Session session = sessionFactory.openSession();
         Transaction transaction = session.beginTransaction();
         //插入
         Student student=new Student();
         student.setId(1);
         student.setAge(20);
         student.setName("扣扣");
         student.setNumber("1224832");
         session.save(student);
         //查询
         Student stu=(Student) session.get(Student.class, 1);
         System.out.println(stu.getId()+":"+stu.getName()+":"+stu.getNumber()
                             +":"+stu.getAge());
         transaction.commit();
         session.close();
         sessionFactory.close();
     }
 }